1. Field of the Invention
The present invention relates to a lens apparatus, and more particularly, to a lens apparatus for correcting a change in an angle of field in a focus operation by driving zoom lens unit, and to a camera system including the lens apparatus.
2. Description of the Related Art
In a conventional zoom lens, it is known that an angle of field of an image is changed due to driving of a focus lens when a focus operation is performed. When the zoom lens is not operated, the image is moved because of a change in the angle of field due to the focus operation (a change in the angle of field occurs) in such photography that the focal point in the image is moved from a subject to another subject. Therefore, there is proposed a lens unit having an angle-of-field correction function that is a technology of eliminating the change in the angle of field by activating zooming.
For instance, Japanese Patent Application Laid-Open No. H10-282396 discloses a technology of correcting the change in the angle of field due to driving of the focus lens by driving a zoom lens. Japanese Patent Application Laid-Open No. 2000-352655 discloses the angle-of-field correction function for correcting the change in the angle of field due to driving of the focus lens by driving the zoom lens and discloses a technology of inhibiting the angle-of-field correction function.
However, in the conventional technologies disclosed in Japanese Patent Application Laid-Open No. H10-282396 and Japanese Patent Application Laid-Open No. 2000-352655, the change in the angle of field due to focus driving is not corrected when zoom and focus are being operated simultaneously. It is desirable that the angle of field intended by a photographer be reflected on the image displayed by operation using a zoom operation unit. However, if the change in the angle of field due to focusing varies at a rate that cannot be neglected with respect to a change in the angle of field due to a zooming operation, an operation amount in the zoom operation unit and the change in the angle of field in the image are not agreed with each other. Then, an image intended by the photographer cannot be generated.